appendix a

 

An Ordinary Kriging Example using the Geostatistical analyst extension


A step-by-step example of the Ordinary Kriging process using the Geostatistical Wizard.  In preparation, customize your toolbar to display the Geostatistical Wizard.  For more examples and details of the process refer to ESRI (2003).

  1. 1.    From the Geostatistical Wizard drop down menu in the Tool Bar, select the Geostatistical Wizard option.  At any point in the process you can use the BACK Button to view the previous screen and change parameters.

  2. 2.    In this first dialog box, select the interpolation method, in this case Kriging; the data input File (e.g. Locations shape file); and the attribute to be modeled (e.g. Litter = 1 hour fuel type). Click NEXT>>


  1. 3.Select the Kriging method (Ordinary) and open its folder by clicking on the “+” sign; select the type of output surface desired (e.g. Predictions); selecting one of the other output types will produce a map of that statistical parameter. In this case there will be no de-trending and no transformations. Click NEXT >>

  2. 4.This window shows the calculated experimental variogram points.  The number of points displayed and the final curve fitting will depend upon the options selected on this page, especially the lag size and number; and whether or not a directional variogram is applied (the azimuth).  The Madera data were originally fit to a Gaussian Curve as selected here.  You are also allowed the option to create models using more than one curve (Model options 2 & 3).  The equation of the model selected will be displayed in the lower left corner.  Click NEXT >>


  1. 5.This window allows you to preview the surface model output; and set the number of neighbors used in the calculation; and set the size of the search ellipse. Click NEXT >>



  1. 6.View the statistical output with the option to save the data as a KML file: view plots of the Standard Error, Q-values, and Predicted vs. Measured values. Click FINISH>>

  2. 7. Displays a summary of the modeling parameters which can also be saved as a KML file. Choose the SAVE option or Click OK to continue>>


  1. 8.You will be asked if you want to add the results to the map as a layer. Click YES>>. 


  1. 9.The layer is added but extends beyond the actual extent of the study area.  You must first convert this output to a Raster Layer (Right Click on the layer>Data>Export to Raster).  This creates an ESRI raster grid. 


  1. 10.  Next, use the Spatial Analyst to extract the true study area data.  Select the Spatial Analyst from the toolbox: Spatial Analyst>Extraction>Extract by Mask. Input the ESRI grid as the raster file and the mapbase polygon as the mask.


  1. 11. Change the symbology as needed.


  1. 12. Produce the final map layout.

 



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